Current Speed

Current speed influences the vertical position that a fish can hold. The
faster the current the less likely a fish can hold close to the surface.
It must seek a place resting in the slower deeper currents; consequently,
its vision window is enlarged. The slower the current the shallower a fish
can hold, and its

vision window is diminished. But the faster currents have a more broken
surface that obscures the fish’s vision; therefore, its outside
world is more distorted in faster flows. Slower currents have calmer
surfaces which are easier for the fish to see through.